1. Field of the Invention
The invention relates to resins which are suitable for use as pigment paste resins and are dilutable in water following neutralization. The resins are obtainable by reacting hard resins based on aldehydes or ketones with a binderlike polycarboxyl component which is dilutable in water following neutralization.
2. Description of Related Art
Hard resins based on aldehydes or ketones, generally referred to in simplified form in the art as aldehyde resins or ketone resins respectively, have been known for a long time. Such resins are formed when ketones are condensed under the catalysis of alkali; especially notable is the resin derived from cyclohexanone. Such resins are described, i. a., in "The Chemistry of Synthetic Resins" by Carleton Ellis, New York 1935, page 557 et seq. Other solid and fusible resins are produced from the cocondensation of, e.g., cyclohexanone and formaldehyde with mild alkali (ibid., page 559). These hard resins are important base materials for nitrocellulose lacquers and alkyd resin varnishes because of their specific coatings properties, such as light color, resistance to hydrolysis and yellowing, compatibility with other coatings binders, and excellent solubility in polar organic solvents. In specific applications too, for instance as a base resin for solvent borne universal pigment pastes, they have in recent years acquired great practical significance.
In view of the demand for environmentally friendly coating materials, however, aldehyde and ketone resins have a substantial disadvantage from the point of view of paint manufacturers and users: in particular they are insoluble in water.
Only a few attempts to prepare stable aqueous dispersions on the basis of such water-insoluble aldehyde and ketone resins are known from the patent literature and are described, for example, in DE-A 34 06 474, where co-components include a protective colloid and specific copolymers.